The blood platelets Definition The blood platelets are
The blood platelets Definition : The blood platelets are the smallest cell in the blood are important in the hemostatic processes
Synthesis: (1) The blood platelets are originated from megakaryocyte in the bone marrow (2)the half life time of The blood platelets about 8 -11 days =average 10 days in the circulating blood (3) The blood platelets are mostly eliminated by the macrophage in the spleen
Morphology of platelets : (1)The cytoplasm stains pale blue and contain few small , reddish purple granules. (2)non nucleated.
2 -the normal shape of the blood platelets (1)the outer cell membrane (2)the cytoplasmic microtubules are present under the cell membrane wall in non stimulating cell and is essential for maintenance of the discoid shape and also important for change the shape and contractility during the activation of The blood platelets (4) The blood platelets contain 2 types of the granules 1)alpha granules 2)dense granules
1)alpha granules are storage site proteins that contain: A. platelet specific proteins (B-thromboglobulin and PF 3) C. von willibrand factor D. fibrinogen E. fibronectin F. platelet derived growth factor for stimulate the mitogenesis and the vessel repair 2)dense granules are storage sites for Ca++, serotonin, ADP and ATP
3 -the function of the thrombocytes (1)the main function of the blood platelets is to maintain the homeostasis by: 1) blood platelets interact with endothelial cells by strengthen the endothelium of the blood vessels so maintain the vascular integrity So the thromocytopenia cause petechiae, eccymosis and bleeding from the body surface 2) blood platelets play an important role in the blood coagulation by providing the PF 3 and carrying coagulation factors on their surface and provide the reaction site for such in vivo interaction 3) blood platelets essential for the clot retraction which depend on their contractile protein system
(2) blood platelets has role in the inflammatory response through releasing of inflammatory mediators as : 1)cationic protein 2)vasoactive amines 3)prostaglandins 4)histamines 5)collagenase 6)elastase That initiate or contribute to persistence of inflammatory response (3) blood platelets have little phagocytic function of the small particles and bacteria in human (4) blood platelets stimulate the mitogenesis and blood vessel repair by releasing PDGF (5)the B-thromboglobulin released from alpha granules acts as chemotactic agent for the granulocytes
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